B&W Associates of Michigan City, Indiana manufactured the B&W Lie Detector shown here, during the early 1950's. This model is identical to the instrument currently used by Cleve Baxter in his ongoing experiments to determine if plants emit Galvanic Skin Response (G.S.R.) activity. The only function of the Model 8AC is to measure G.S.R. activity. The recording of G.S.R. activity had not been integrated into these early polygraph instruments, thus the G.S.R. sensitivity dial on the left side of the instrument was manually controlled by the examiner to set sensitivity at a perceived norm. The centering dial on the right side of the instrument was used to bring the G.S.R. on the instrument into calibration. The meter counts units of G.S.R, and was a very sensitive for its time. The Model 8AC also uses a automatic/manual switch which may be used if the examiner chooses to adjust the sensitivity manually prior to the first relevant question. The examiner had the option of using the automatic setting early in the test.

When in operation, a "Deception Indicated" (DI) reading is established when the pen moves above the 'CENTER' operational area on the meter. The 8AC utilizes only two fingerplates, and it is this theory that started the debate between measuring G.S.R. activity, verses the first studies in voice stress analysis.

The B&W Lie Detector shown here was used until just recently, and is still considered a reliable instrument for determining deception.


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